The Meteorology, Climatology and Geophysics Agency (BMKG) has warned residents across the archipelago about the potential of extreme weather ahead of the rainy season in October.

Agency head Dwikorita Karnawati said in a statement on Tuesday that the rainy season was expected to start between October and December depending on the region, with the peak to occur from January to February 2019.

The agency has been monitoring a weather phenomenon called Madden Julian Oscillation, which occurs in the air surrounding the archipelago, bringing extra water vapor to form clouds in the sky. A decrease in dry and cold air movement from Australia will also affect the upcoming weather.

“Such a phenomenon will push for an increase in the potential of rain clouds forming,” Dwikorita said.

She warned people living in nine provinces — Aceh, West Sumatra, Bengkulu, North Kalimantan, Central Sulawesi, Southeast Sulawesi, Maluku, West Papua and Papua — to prepare for heavy rains accompanied by thunder and strong winds in the next three days.

Moreover, the BMKG also warned fisherfolk and those living in coastal regions to watch for high waves with a height between 2.5 to 4 meters from September to December.

“During the rainy season, people should also be on the look out for natural disasters, such as floods, landfalls, strong winds and tornadoes,” Dwikorita said.